Charge distribution gun

ABSTRACT

A charge distribution gun having a charging, corona region through which air flows to carry charges to a gun outlet opening to a zone where charge distribution is desired. Useful, for example, to suppress airborne dust, the gun includes an arrangement for preventing formation of a conductive or partly conductive path on exterior surfaces by the collection of charged particles thereon. A jacket encircling the charge flow path directs air to an annular opening and a porous end plate, both encircling the gun outlet. Air escaping through the annular opening reduces the settling of charged particles from the gun outlet back onto nearby gun surfaces. The porous plate defines a nonconductive outer surface encircling the gun outlet. Air forced through the pores of the plate maintain the surface clean of charged particles. No conductive path across the plate is formed; corona or contact discharge of charges at the gun output is prevented.

United States Patent Hanley et al.

[54] CHARGE DISTRIBUTION GUN [72] Inventors: John P. Hanley, West Paterson; Robert W. Seaman, Morris Plains, both of NJ.

[73] Assignee: Gourdine Systems, Inc., Livingston,

[22] Filed: Nov. 5, 1970 [21] Appl. No.: 87,253

[ Aug. 8, 1972 Primary Examiner-L. T. Hix Attorney-Brumbaugh, Graves, Donohue & Raymond [57] ABSTRACT A charge distribution gun having a charging, corona region through which air flows to carry charges to a gun outlet opening to a zone where charge distribution is desired. Useful, for example, to suppress airborne dust, the gun includes an arrangement for preventing formation of a conductive or partly conductive path on exterior surfaces by the collection of charged particles thereon. A jacket encircling the charge flow path directs air to an annular opening and a porous end plate, both encircling the gun outlet. Air escaping through the annular opening reduces the settling of charged particles from the gun outlet back onto nearby gun surfaces. The porous plate defines a nonconductive outer surface encircling the gun outlet. Air forced through the pores of the plate maintain the surface clean of charged particles. No conductive path across the plate is formed; corona or contact discharge of charges at the gun output is prevented.

12 Claims, 3 Drawing Figures I I I l I I l I 1 I I I I +1 ii I li 26 1 CHARGE DISTRIBUTION GUN BACKGROUND OF THE INVENTION Generally, this invention relates to charge distribution apparatus, and more particularly, to improvements for preventing the establishment of a conductive or partly conductive path along a charge distribution gun through particles collected on outer surfaces of the gun.

Charge distribution arrangements or guns have been proposed for various purposes. For example, suppressing airborne dust or other particular contaminant by introducing charged particles into a contaminated region is the subject of the copending application Ser. No. 87,235, filed Nov. 5, 1970, and assigned to the assignee of the instant invention. There an electrogasdynamic (EGD) gun and its method of use for this purpose are described. Where the airborne particles to be suppressed or the seed particles carrying charges into the contaminated zone are conductive, or partly conductive, a reduction in the effectiveness of the EGD method of suppression by charge distribution has been noted. Charged contaminant particles collecting on exterior surfaces of the gun can form a conductive path from the gun outlet to ground. The coated surfaces near the gun outlet are connected by the conductive path to a potential differing greatly from the potential of the charge stream leaving the outlet. When this occurs, charged particles leaving the gun outlet lose their charges by corona discharge at the outlet or by contact discharge to the nearby conductively coated surfaces.

Even if dielectric gun surfaces are given a configuration increasing the surface distance along the outside of the gun, for example, to ground, the undesired path still can be established. Ordinarily, charged particles continue to come to rest on a dielectric surface until a saturation charge is reached at the surface. In the case of conductive or partly conductive particles, charge saturation often is not reached because the particle coating itself conducts away the charges before saturation. More charged particles are attracted to the gun surfaces; the surface becomes more conductive.

SUMMARY OF THE INVENTION In view of the difficulties noted above, it is a primary object of this invention to provide apparatus avoiding the establishment of an electrical path along the outside of a charge distribution arrangement.

Additionally, an object of the invention is to prevent the establishment of an electrical path from proximate a charge distribution outlet to a point of differing electrical potential, thereby reducing charge loss at the gun outlet.

A further object of the invention is to provide apparatus for a charge distribution gun to prevent the formation of a conductive path through particles collecting on exterior surfaces of a charge distribution arrangement by directing fluid flow to oppose particle deposition.

Yet another object of the invention is to provide an improved charge distribution arrangement in which fluid flow prevents the deposition of particles on surfaces near the charge outlet to prohibit the establishment of an electrical potential at those surfaces.

The foregoing objects are achieved, in accordance with the invention, by maintaining an exterior surface of a charge distribution arrangement substantially free of deposited particles. An annular porous plate encircles the charge outlet forming a dielectric part of the outer gun surface. Fluid forced through the porous plate, outward, prevents particle deposition on the outer surface of the plate. No conductive path forms on the plate, and no potential at the plate surface results. Forced through an annular opening also surrounding the outlet, air flow substantially prevents the roll back of charged particles to nearby gun surfaces. Also, a continuous deposited electrical path cannot be formed across the annular opening to the gun outlet.

Where, as in the case of the EGD gun described below, the charge distributor includes a long channel opening into the area where charges or charged particles are to be distributed, a jacket may be supported about the channel forming member, to supply fluid to the channel output end. There, the fluid is forced through the annular opening and the porous plate. A compact, self-cleaning gun arrangement is the result.

In the specific preferred embodiment described below, the deposited path from near the charge outlet would lead to ground. Although this is likely the most common difficulty, it may be that elements at another potential are exposed and the deposition of a conductive path to one of those elements would produce, near the charge outlet, a potential other than ground. The mention of ground potential in the discussion that follows is thus exemplary only. Also, the particles which settle onto surfaces to form a conductive path may be either or both airborne particles in the zone into which thecharge outlet opens and charge carrying seed particles emitted by the charge distributing apparatus. For example, charged particles sprayed from a gun, for painting, or other spray coating, may settle back onto gun surfaces to cause the problems overcome by this invention.

IN THE DRAWINGS FIG. 1 is a fragmentary cross-sectional view, which shows a charge distribution gun with an annular passage and a porous end plate, both encircling the gun outlet.

FIG. 2 is an enlarged fragmentary elevational view, along line 2-2 of FIG. 1, with parts broken away for clarity, and illustrates the gun output end, an associated jacket member, the porous end plate, and the members forming the annular opening.

FIG. 3 is a diagrammatic illustration of a gun supported for dust suppression, absent the gas flow provisions according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENT In FIG. 1, a charge distribution gun 10, here an EGD gun, includes a channel member 11 with an interior channel 12 ending at an outlet 13 formed by a nozzle 14 at the gun output end. The gun 10 also includes a charging region (not shown in FIG. 1) at its opposite end. Not a part of the invention, the upstream charging region of the gun 10 may, typically, include a corona discharge needle electrode, and one or more attractor electrodes cooperating, when energized by a high potential, to form a corona discharge region.

An EGD gun arrangement for use in dust, or other airborne contaminant suppression, as described in the copending application mentioned above, is shown in FIG. 3. There the channel 12 opens into a metallic enclosure 15, connected to ground. The corona discharge needle and'attractor electrode are shown at 16 and 17, respectively. Compressed air is supplied into the channel 12 from a line 18. The movement of the compressed air down the channel carries charges from the corona region into the dusty or contaminated zone within the enclosure 15. Fine liquid droplets may be suspended in the gaseous stream by spraying liquid, water for example, from a line 20 into the channel 12,

- just ahead of the corona region. The gas and droplet combination forms a fine aerosol, the droplets serving as seed particles carrying charges to the zone to be treated.

Charged contaminant particles and seed particles are attracted to nearby surfaces, including the surfaces of the gun. If the contaminant or seed particles are at all conductive, a conductive path 24 will form from near the outlet 13, along the exterior gun surface, to the grounded enclosure 15. Via the conductive path 24, ground potential is established near the guns charge outlet 13.

Charges escaping from the outlet 13 are at a high potential. In particular, when the charges have undergone an electrogasdynamic energy exchange, decelerating against an axial opposing electric field in coming to the outlet 13, the potential of the charge stream at the outlet will be extremely high. The deposition of a conductive path from ground or other potential to locations near the outlet 13 can establish a potential difference at the outlet sufficient to cause a secondary corona discharge by which emerging charges are neutralized. Grounded or nearly grounded surfaces at the outlet 13 also attract charges or charged seed particles leaving the outlet 13. By contact discharge the effectiveness of the dust or contaminant suppressing arrangement is reduced.

The additional gas flow provisions of FIGS. 1 and 2, mounted on the exterior of the channel member 11, prevent the formation of a continuous electrical path from near the channel outlet to exposed elements at ground. An exterior jacket 25 extends along the channel member 11, encircling the member 11 and slightly radially spaced from the exterior surface thereof. A gas supply passage 26 is formed. Gas ports 27 open into the passage and are threaded at 28 for connection to a suitably chosen gas or compressed air supply line (not shown).

Two rings 29 and 30 close and support the jacket 25 at one end. At the guns output end, the noule 14, which communicates with and forms a part of the channel 12, is smaller in diameter than the channel member 1 1. Encircling the nozzle 14, an annular manifold block 31 is supported at a shoulder 32 on the end of the channel member 11 and extends forward. A flange 33 on the manifold block 31 supports the forward end of the zle define an annular opening 36 surrounding the tip of the nozzle and inclined slightly radially outwardly in the direction of gas flow.

Supported between a shoulder on the hub 34 and the extreme end of the jacket 25, an annular dielectric porous disc 38 also surrounds the gun output 13. A ring 39 and suitable screws or other fasteners hold the porous disc in place on the jacket end. A dielectric surface 37, the outer surface of the disc 38, encircles the path of charge flow and forms a part of the outer surfaces of the gun 10. Deposited paths from near the gun outlet to ground must cross the surface 37.

Several passages 40 extend through the manifold block 31, placing in communication the passage 26 and a chamber or plenum 41 formed between opposed axially extending surfaces of the manifold block 31 and the nozzle 14. The annular opening 36 extends from the chamber 41 to the exterior of the gun. Three further openings 42 open axially through a part of the manifold block 31 from the chamber 41 into another chamber or plenum 44 directly beneath the porous plate 38. Air under pressure is supplied to the annular opening 36 and to the interior surface of the plate 38.

In operation, a fine, charged aerosol of air and water droplets is produced, charged in the corona region, and passed down the channel 12 to the outlet 13. Charged particles are introduced into the region at the outlet of the gun just as in the arrangement according to FIG. 3, but compressed air also is supplied into the passage 26 through the ports 27. Air moves down the passage 26 through the radial passages 40, into the chamber 41, and escapes through the annular opening 36. An air shroud completely encircling the charge flow path from the gun outlet is formed.

Charged particles escaping the outlet are prevented from returning to the face of the gun across the flow of air escaping through the annular passage 36. The encircling air shroud aids movement of charges forward as desired while preventing such roll back of charged particles. In addition, because they are unable to bridge the opening 36, deposited particles cannot form a path from near the outlet 13 and back to ground. This helps prevent an undesired potential produced on the face of the nozzle 14 near the outlet 13.

Air from the chamber 41 flows through the passages 42 into the chamber 44 and escapes through the pores of the disc 38. Charged particle deposition on the dielectric surface 37 is prevented. This continuous selfcleaning prevents the deposition of a conductive path across the face of the gun and prevents the formation of a substantial surface area at undesired potential near the gun outlet capable of causing contact discharging. Because a conductive or partly conductive path is not established to near the gun outlet the likelihood of secondary corona discharge, arcing, or contact discharge, shorting the gun to ground, is reduced substantially.

The air shroud formed by air from the annular opening aids the cleansing of the porous disc surface by preventing charged seed particles movement to surface 37 immediately upon emission from the gun output. Together, the annular opening, the porous disc, and the fluid supply provisions provide a compact addition to the gun. They may be supplied air from the same source as the main gun channel and may be operated each time the gun is used.

As noted above, the inventive features described may be used in various applications. In addition to the specific preferred embodiment described above, modifications may be made as desired without departure from the spirit and scope of the invention defined in the appended claims.

We claim:

1. A charge distribution arrangement comprising charge production means, means for moving charges from the charge production means out of the distribution arrangements and particle deposit preventing means for preventing the establishment of an at least partly conductive path through particles on exterior surfaces of the distribution arrangement, the deposit preventing means including means for passing fluid outward from within means defining outer surfaces of the arrangement to direct fluid past an exterior surface area to prevent particle build-up at the area, the fluid passing means comprising a porous member defining a dielectric part of the outer surface of the arrangement and encircling the flow of charges to prevent deposition of an electrical path across said part of the outer surface by the passage of fluid therethrough.

2. The arrangement according to claim 1, including an output opening through which charges escape, and wherein the fluid passing means further comprises an annular opening encircling the output opening, whereby passage of fluid outwardly through the annular opening substantially prevents the return of charges across the path of fluid passing from annular opening near the output opening to nearby surfaces of the arrangement.

3. The arrangement according to claim 1, including an output opening through which charges escape, and wherein the fluid passing mean further comprises an annular opening encircling the output opening and means for directing fluid through the annular opening, whereby particles are prevented from bridging the annular opening.

4. The arrangement according to claim 1, further comprising a jacket encircling the path of charge flow, and having an interior in communication with the fluid passing means, and inlet means for directing fluid into the jacket.

5. The arrangement according to claim 4, further including an output orifice, said porous member being an annular porous end plate encircling the output orifice, and wherein the jacket interior is in communication with the undersurface of the plate to provide fluid passage through the plate, whereby there is prevented the establishment of an electrical path across the plate by the accumulation of particles thereon.

6. The arrangement according to claim 4, further including an output orifice, an annular opening encircling the output orifice, and wherein the jacket interior is in communication with the annular opening, to provide fluid passage through the annular opening, whereby there is prevented the establishment of an electrical path by the accumulation of particles across the annular opening.

. 7. The arrangement according to claim 1, further including a corona discharge region, means for entraining charge carrier particles in a gas stream through the corona region, a channel for directing the combined gas and charged particle stream from the corona region to an out ut nin of the c el, 'd ass'n means coinpris ifig m eans provi d i r i g a fl iiid il dweappbs ing the attraction of charged particles back to the channel forming member near the output opening thereof.

8. The arrangement according to claim 7, wherein the porous member comprises a porous disc encircling the channel output opening for the passage of gas therethrough to prevent the collection of a continuous, circuit-forming collection of particles thereon.

9. The arrangement according to claim 7, wherein fluid passing means includes an annular opening encircling the output opening of the channel and means for supplying fluid through the annular opening in path of flow surrounding the flow of charges and substantially preventing charge roll back across the path of fluid flow to nearby surfaces.

10. The arrangement according to claim 7, wherein the fluid passing means includes an annular opening and said porous member is a porous disc, both opening and disc encircling the channel output opening for the passage of gas therethrough substantially to prevent charge movement near the output opening to nearby surfaces and to prevent the collection of particles in a continuous conductive path from near the output opening, across the annular opening and the disc, to an element at an undesired potential.

11. The method of preventing the deposition of a continuous conductive path by the collection of particles on exterior surfaces during charge emission by a charge distribution arrangement; the method including the steps of flowing charges along a predetermined path, providing fluid flow provisions forming at least part of the exterior surfaces of the charge distribution arrangement, supplying fluid into the fluid flow provisions, and expelling fluid from within the fluid flow provisions outward past the exterior surface to prevent the collection of particles, the step of fluid expulsion including providing a porous member in entirely encircling relation to the flow of charges as a part of the fluid flow provisions forming exterior surfaces, and forcing fluid from within the fluid flow provisions through the porous member to prevent the collection of particles on the surface of the porous member.

12. The method according to claim 11, wherein the step of fluid expulsion includes forcing fluid outward in an annular path encircling the path of charges leaving the distribution arrangement. 

1. A charge distribution arrangement comprising charge production means, means for moving charges from the charge production means out of the distribution arrangements and particle deposit preventing means for preventing the establishment of an at least partly conductive path through particles on exterior surfaces of the distribution arrangement, the deposit preventing means including means for passing fluid outward from within means defining outer surfaces of the arrangement to direct fluid past an exterior surface area to prevent particle build-up at the area, the fluid passing means comprising a porous member defining a dielectric part of the outer surface of the arrangement and encircling the flow of charges to prevent deposition of an electrical path across said part of the outer surface by the passage of fluid therethrough.
 2. The arrangement according to claim 1, including an output opening through which charges escape, and wherein the fluid passing means further comprises an annular opening encircling the output opening, whereby passage of fluid outwardly through the annular opening substantially prevents the return of charges across the path of fluid passing from annular opening near the output opening to nearby surfaces of the arraNgement.
 3. The arrangement according to claim 1, including an output opening through which charges escape, and wherein the fluid passing mean further comprises an annular opening encircling the output opening and means for directing fluid through the annular opening, whereby particles are prevented from bridging the annular opening.
 4. The arrangement according to claim 1, further comprising a jacket encircling the path of charge flow, and having an interior in communication with the fluid passing means, and inlet means for directing fluid into the jacket.
 5. The arrangement according to claim 4, further including an output orifice, said porous member being an annular porous end plate encircling the output orifice, and wherein the jacket interior is in communication with the undersurface of the plate to provide fluid passage through the plate, whereby there is prevented the establishment of an electrical path across the plate by the accumulation of particles thereon.
 6. The arrangement according to claim 4, further including an output orifice, an annular opening encircling the output orifice, and wherein the jacket interior is in communication with the annular opening, to provide fluid passage through the annular opening, whereby there is prevented the establishment of an electrical path by the accumulation of particles across the annular opening.
 7. The arrangement according to claim 1, further including a corona discharge region, means for entraining charge carrier particles in a gas stream through the corona region, a channel for directing the combined gas and charged particle stream from the corona region to an output opening of the channel, the fluid passing means comprising means providing a fluid flow opposing the attraction of charged particles back to the channel forming member near the output opening thereof.
 8. The arrangement according to claim 7, wherein the porous member comprises a porous disc encircling the channel output opening for the passage of gas therethrough to prevent the collection of a continuous, circuit-forming collection of particles thereon.
 9. The arrangement according to claim 7, wherein fluid passing means includes an annular opening encircling the output opening of the channel and means for supplying fluid through the annular opening in path of flow surrounding the flow of charges and substantially preventing charge roll back across the path of fluid flow to nearby surfaces.
 10. The arrangement according to claim 7, wherein the fluid passing means includes an annular opening and said porous member is a porous disc, both opening and disc encircling the channel output opening for the passage of gas therethrough substantially to prevent charge movement near the output opening to nearby surfaces and to prevent the collection of particles in a continuous conductive path from near the output opening, across the annular opening and the disc, to an element at an undesired potential.
 11. The method of preventing the deposition of a continuous conductive path by the collection of particles on exterior surfaces during charge emission by a charge distribution arrangement; the method including the steps of flowing charges along a predetermined path, providing fluid flow provisions forming at least part of the exterior surfaces of the charge distribution arrangement, supplying fluid into the fluid flow provisions, and expelling fluid from within the fluid flow provisions outward past the exterior surface to prevent the collection of particles, the step of fluid expulsion including providing a porous member in entirely encircling relation to the flow of charges as a part of the fluid flow provisions forming exterior surfaces, and forcing fluid from within the fluid flow provisions through the porous member to prevent the collection of particles on the surface of the porous member.
 12. The method according to claim 11, wherein the step of fluid expulsion includes forcing fluid outward in an annular path encircling the path of Charges leaving the distribution arrangement. 